There is obviously going to be more collections. This collection covers the first two generations of the series minus Rondo of Blood. I guess the next one will have Rondo, Symphony, the last GB-game Legends and the two N64 Castlevanias, the third will have the three GBA-games plus Harmony of Dissonance and the fourth one will have the three DS-titles and Curse of Darkness. But i think that will all depend on if this one sells or not
I would do a backflip for N64 Castlevanias, but I'm betting they will only focus on Canon games. I'm also betting it will end with a new Castlevania.